1. Field of the Invention
This invention relates to railway car body and methods of making the same and is applicable to the manufacture of railway and other track-guided vehicle bodies, including bodies for monorail and mag-lev (magnetic levitation) vehicles, as well as to railway powered cars, non-powered cars and locomotives, particularly to passenger cars for railway vehicles operating at high speed.
2. Description of the Prior Art
Conventionally, railway car body structures have been formed of steel by , for example, connecting longitudinal frame members and transverse frame members and then connecting outside sheets to the outside of the frame. In such a structure produced using stainless steel as the outside sheets, for example, 3-dimensional joints are employed in order to improve strength between the frame members and the outside sheets as disclosed in JP-B-62-35937. It is also known to produce a railway car body structure using light metal, such as aluminum alloy. The aim is to reduce the number of man-hours in production of the car body structure and to improve stiffness of the car body structure, using pre-shaped members in which frame members and the outside sheet are integral. For example, body structures with extruded shaped members are described on pages 70 to 72 of "Light Metal Railway Vehicle Committee Report 0036 No. 3", published in 1978 by the Japanese Railway Vehicle Industry Association, pages 70-72.
Another type of pre-formed metal member is a sandwich construction having two metal sheets that are spaced apart and are bonded to opposite faces of a cellular metal core by an adhesive or by brazing. The core may be a formed metal or a honeycomb construction, which is itself, for example, produced by brazing together of corrugated sheet. Such sandwich constructions have been proposed for use in railway car bodies, but for the most part not as structural members of such car body structures i.e. members contributing substantially to the structural strength of the car body.
In Japanese utility model publication no. 60-179569, honeycomb sandwich panels are provided as stiffeners of the outside plates of the car body, by adhesively bonding the honeycomb panel to the interior face of the outside plate. Here, the honeycomb panels are acting as reinforcements against bending of the outside plate.
In Japanese utility model publication no. 54-183007, honeycomb panels are proposed as floorboards, which rest upon the floorplate constituting the underframe of the vehicle body however, the honeycomb panel does not act as a structural member, and is connected to the floorplate by adhesive bonding.
Japanese utility model publication no. 63-18372 however proposes the use of a honeycomb panel as a structural member in the floorplate of a railway car body, with the panel connecting extruded members which constitute the side sills of the car body. The honeycomb panels are connected by rivetting to the extruded members. At the present time, rivetting is an unsuitable connection method for structural members of railway car bodies, at least at visible regions, and also cannot provide a hermetic joint between structural members.
A further disadvantage of rivetting resides in the amount of labor required, which is greater than that for welding.
The prior art discussed above therefore does not provide solutions to the problem of reduction in weight of railway car body structures. With the increase in running speeds of railway vehicles, problems such as increase of impact on the rails and increase of noise, as well as increase of power consumption can be mitigated by reduction of the weight of the railway car body structure. Weight reduction is attempted by reducing the thickness of the frame members and of the outside sheet members, but the amount of reduction is limited by the need to maintain stiffness of the body structure.
In the case of pre-shaped members made of light alloys by extrusion, there is a technical limit to the reduction of the thickness of the shaped member, and furthermore if thickness is reduced too much, out-of-plane bending stiffness and shearing stiffness is reduced, so that there is a need for a large number of reinforcing members thereby also increasing the labor required in manufacturing of the vehicle.
A further problem with high speed railway vehicles is that inside a tunnel there may be drastic outside pressure changes, which may occur rapidly, particularly when vehicles pass each other inside the tunnel. To prevent such a pressure change from being transmitted to the interior of the vehicle which is unpleasant for the passengers, the body structure can have a generally hermetic structure. However, the body structure must then resist not only the load of the passengers and the various equipment attached to it and its own weight, but also the pressure load due to the exterior pressure changes. Thus, an increase in stiffness of the body structure is required and an improvement in strength against the pressure load must be achieved.